net/netfilter/nf_conntrack_helper.c

   1 /* Helper handling for netfilter. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   5  * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/stddef.h>
  18 #include <linux/slab.h>
  19 #include <linux/random.h>
  20 #include <linux/err.h>
  21 #include <linux/kernel.h>
  22 #include <linux/netdevice.h>
  23 #include <linux/rculist.h>
  24 #include <linux/rtnetlink.h>
  25
  26 #include <net/netfilter/nf_conntrack.h>
  27 #include <net/netfilter/nf_conntrack_l3proto.h>
  28 #include <net/netfilter/nf_conntrack_l4proto.h>
  29 #include <net/netfilter/nf_conntrack_helper.h>
  30 #include <net/netfilter/nf_conntrack_core.h>
  31 #include <net/netfilter/nf_conntrack_extend.h>
  32
  33 static DEFINE_MUTEX(nf_ct_helper_mutex);
  34 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  35 static unsigned int nf_ct_helper_hsize __read_mostly;
  36 static unsigned int nf_ct_helper_count __read_mostly;
  37 static int nf_ct_helper_vmalloc;
  38
  39
  40 /* Stupid hash, but collision free for the default registrations of the
  41  * helpers currently in the kernel. */
  42 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
  43 {
  44         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
  45                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
  46 }
  47
  48 static struct nf_conntrack_helper *
  49 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  50 {
  51         struct nf_conntrack_helper *helper;
  52         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  53         struct hlist_node *n;
  54         unsigned int h;
  55
  56         if (!nf_ct_helper_count)
  57                 return NULL;
  58
  59         h = helper_hash(tuple);
  60         hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
  61                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
  62                         return helper;
  63         }
  64         return NULL;
  65 }
  66
  67 struct nf_conntrack_helper *
  68 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
  69 {
  70         struct nf_conntrack_helper *h;
  71         struct hlist_node *n;
  72         unsigned int i;
  73
  74         for (i = 0; i < nf_ct_helper_hsize; i++) {
  75                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  76                         if (!strcmp(h->name, name) &&
  77                             h->tuple.src.l3num == l3num &&
  78                             h->tuple.dst.protonum == protonum)
  79                                 return h;
  80                 }
  81         }
  82         return NULL;
  83 }
  84 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
  85
  86 struct nf_conntrack_helper *
  87 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
  88 {
  89         struct nf_conntrack_helper *h;
  90
  91         h = __nf_conntrack_helper_find(name, l3num, protonum);
  92 #ifdef CONFIG_MODULES
  93         if (h == NULL) {
  94                 if (request_module("nfct-helper-%s", name) == 0)
  95                         h = __nf_conntrack_helper_find(name, l3num, protonum);
  96         }
  97 #endif
  98         if (h != NULL && !try_module_get(h->me))
  99                 h = NULL;
 100
 101         return h;
 102 }
 103 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
 104
 105 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 106 {
 107         struct nf_conn_help *help;
 108
 109         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
 110         if (help)
 111                 INIT_HLIST_HEAD(&help->expectations);
 112         else
 113                 pr_debug("failed to add helper extension area");
 114         return help;
 115 }
 116 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 117
 118 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 119                               gfp_t flags)
 120 {
 121         struct nf_conntrack_helper *helper = NULL;
 122         struct nf_conn_help *help;
 123         int ret = 0;
 124
 125         if (tmpl != NULL) {
 126                 help = nfct_help(tmpl);
 127                 if (help != NULL)
 128                         helper = help->helper;
 129         }
 130
 131         help = nfct_help(ct);
 132         if (helper == NULL)
 133                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 134         if (helper == NULL) {
 135                 if (help)
 136                         rcu_assign_pointer(help->helper, NULL);
 137                 goto out;
 138         }
 139
 140         if (help == NULL) {
 141                 help = nf_ct_helper_ext_add(ct, flags);
 142                 if (help == NULL) {
 143                         ret = -ENOMEM;
 144                         goto out;
 145                 }
 146         } else {
 147                 memset(&help->help, 0, sizeof(help->help));
 148         }
 149
 150         rcu_assign_pointer(help->helper, helper);
 151 out:
 152         return ret;
 153 }
 154 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 155
 156 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 157                          const struct nf_conntrack_helper *me)
 158 {
 159         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 160         struct nf_conn_help *help = nfct_help(ct);
 161
 162         if (help && help->helper == me) {
 163                 nf_conntrack_event(IPCT_HELPER, ct);
 164                 rcu_assign_pointer(help->helper, NULL);
 165         }
 166         return 0;
 167 }
 168
 169 void nf_ct_helper_destroy(struct nf_conn *ct)
 170 {
 171         struct nf_conn_help *help = nfct_help(ct);
 172         struct nf_conntrack_helper *helper;
 173
 174         if (help) {
 175                 rcu_read_lock();
 176                 helper = rcu_dereference(help->helper);
 177                 if (helper && helper->destroy)
 178                         helper->destroy(ct);
 179                 rcu_read_unlock();
 180         }
 181 }
 182
 183 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 184 {
 185         unsigned int h = helper_hash(&me->tuple);
 186
 187         BUG_ON(me->expect_policy == NULL);
 188         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 189         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 190
 191         mutex_lock(&nf_ct_helper_mutex);
 192         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 193         nf_ct_helper_count++;
 194         mutex_unlock(&nf_ct_helper_mutex);
 195
 196         return 0;
 197 }
 198 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 199
 200 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 201                                              struct net *net)
 202 {
 203         struct nf_conntrack_tuple_hash *h;
 204         struct nf_conntrack_expect *exp;
 205         const struct hlist_node *n, *next;
 206         const struct hlist_nulls_node *nn;
 207         unsigned int i;
 208
 209         /* Get rid of expectations */
 210         for (i = 0; i < nf_ct_expect_hsize; i++) {
 211                 hlist_for_each_entry_safe(exp, n, next,
 212                                           &net->ct.expect_hash[i], hnode) {
 213                         struct nf_conn_help *help = nfct_help(exp->master);
 214                         if ((help->helper == me || exp->helper == me) &&
 215                             del_timer(&exp->timeout)) {
 216                                 nf_ct_unlink_expect(exp);
 217                                 nf_ct_expect_put(exp);
 218                         }
 219                 }
 220         }
 221
 222         /* Get rid of expecteds, set helpers to NULL. */
 223         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 224                 unhelp(h, me);
 225         for (i = 0; i < net->ct.htable_size; i++) {
 226                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 227                         unhelp(h, me);
 228         }
 229 }
 230
 231 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 232 {
 233         struct net *net;
 234
 235         mutex_lock(&nf_ct_helper_mutex);
 236         hlist_del_rcu(&me->hnode);
 237         nf_ct_helper_count--;
 238         mutex_unlock(&nf_ct_helper_mutex);
 239
 240         /* Make sure every nothing is still using the helper unless its a
 241          * connection in the hash.
 242          */
 243         synchronize_rcu();
 244
 245         rtnl_lock();
 246         spin_lock_bh(&nf_conntrack_lock);
 247         for_each_net(net)
 248                 __nf_conntrack_helper_unregister(me, net);
 249         spin_unlock_bh(&nf_conntrack_lock);
 250         rtnl_unlock();
 251 }
 252 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 253
 254 static struct nf_ct_ext_type helper_extend __read_mostly = {
 255         .len    = sizeof(struct nf_conn_help),
 256         .align  = __alignof__(struct nf_conn_help),
 257         .id     = NF_CT_EXT_HELPER,
 258 };
 259
 260 int nf_conntrack_helper_init(void)
 261 {
 262         int err;
 263
 264         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 265         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 266                                                   &nf_ct_helper_vmalloc, 0);
 267         if (!nf_ct_helper_hash)
 268                 return -ENOMEM;
 269
 270         err = nf_ct_extend_register(&helper_extend);
 271         if (err < 0)
 272                 goto err1;
 273
 274         return 0;
 275
 276 err1:
 277         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 278                              nf_ct_helper_hsize);
 279         return err;
 280 }
 281
 282 void nf_conntrack_helper_fini(void)
 283 {
 284         nf_ct_extend_unregister(&helper_extend);
 285         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 286                              nf_ct_helper_hsize);
 287 }